From my library...
Everything You Write Has Value
You believe that what you've written today is at best self-indulgent or repetitious, at worst irrelevant. So be it. It's okay to think that. As long as you don't allow your thoughts to stop you from continuing.
Every word that emerges in every writing session has its own contribution to make to your book or project...or life--be it a direct or indirect one. Trust that and stay open to the flow.
I'm not asking you to trust that this word is perfect and that so is this one. I'm asking you to trust that this word forms a part of a larger picture that you will not be able to see until you step back from it--later today, tomorrow, next week, next month or next year.